Silver halide photographic supersensitized emulsions

ABSTRACT

A GREEN-SENSTIVE SILVER HALIDE PHOTOGRAPHIC EMULSION FOR COLOR PHOTOGRAPHIC MATERIALS SUPER-SENSITIZED BY A COMBINATION OF A SPECIFIC BENZIMIDAZOLO OXACARBOCYAMINE DYE AND A SPECIFIC OXACARBOCYAMINE DYE.

SILVER HALIDE PHOTOGRAPHIC SUPERS ENSITIZED EMULSIONS Filed Nov. 24.1972 ll .1. O S 55:52?

WAVELENGTH (nm) United States Patent 3,832,189 SILVER HALIDEPHOTOGRAPHIC SUPER- SENSITIZED EMULSIONS Keisuke Shiba, Masanao Hinata,Akira Sato, Akita Ogawa, and Takashi Ikeda, Kanagawa, Japan, assignorsto Fuji Photo Film Co. Ltd., Kanagawa, Japan Filed Nov. 24, 1972, Ser.No. 309,531 Claims priority, application Japan, Nov. 24, 1971, 46 94,266Int. Cl. G03c 1/14 US. Cl. 96-124 17 Claims ABSTRACT OF THE DISCLOSURE Agreen-sensitive silver halide photographic emulsion for colorphotographic materials super-sensitized by a combination of a specificbenzimidazolo oxacarbocyanine dye and a specific oxacarbocyanine dye.

BACKGROUND OF THE INVENTION Field of the Invention This inventionrelates to a spectrally sensitized silver halide photographic emulsionand particularly to a silver halide photographic emulsionsupersensitized by a combination of two kinds of sensitizing dyes. Moreparticularly, the invention relates to a supersensitized greensensitivesilver halide photographic emulsion for color photographic materials.

Description of the Prior Art Spectral sensitizing techniques ortechniques of extending the sensitive wave length region of a silverhalide photographic emulsion to the longer wave length side byincorporating a certain cyanine dye in a silver halide photographicemulsion are well known in manufacturing photographic light-sensitivematerials.

The spectral sensitization depends upon the chemical structure of thesensitizing dye and various properties of the silver halide emulsionemployed, such as the halogen composition, the crystal habit, thecrystal system, the silver ion concentration, and the hydrogen ionconcentration of the silver halide emulsion. The spectral sensitizationis further influenced by photographic additives incorporated in thephotographic emulsion, such as a stabilizer, an antifoggant, a wettingagent, a precipitant, a color coupler, etc.

In order to sensitize a definite spectral wave length region of aphotographic light-sensitive material, only one kind of sensitizing dyemay be used, but in many cases a combination of two or more kinds ofsensitizing dyes is used. In the case of employing such a combination ofsensitizing dyes, however, it frequently happens that the spectralsensitivity obtained is lower than the sensitivity obtained with theseparate use of each of the sensitizing dyes. However, in certainspecific cases the spectral sensitivity obtained by such a combinationof sensitizing dyes is in an increased super additive manner byemploying a combination of a specific sensitizing dye and one or moreother specific sensitizing dyes. This phenomenon is known assupersensitization. In such a supersensitization, even if the differenceof chemical structure between one sensitizing dye and the othersensitizing dye is slight, the difference in the supersensitizing actionbetween them is frequently quite large. Accordingly, it is known that acombination of sensitizing dyes showing a supersensitizing action canhardly be predicted from the chemical structures thereof alone.

Therefore, in manufacturing photographic emulsions the sensitizing dyesto be used as a combination thereof for supersensitization must be quitecarefully selected. The sensitizing dyes used in the case of applyingsupersensiti- "Ice zation to a silver halide photographic emulsion mustalso have no harmful co-action with other photographic additives andmust have stable photographic properties even during the preservation ofphotographic light-sensitive materials which contain such dyes.

Some photographic additives, when added to a silver halide photographicemulsion, decrease the spectral sensitivity thereof, and examples ofsuch additives are anionic compounds such as light-absorbing dyes havingan anionic group, e.g., a sulfo group; gelatin precipitants having ananionic group, e.g., a sulfo group or carboxyl group; and couplers forcolor photographic materials. In particular, in the case of agreen-sensitive silver halide photographic emulsion for colorphotographic light-sensitive materials, the change of spectralsensitivity when a. supersensitizing combination of dyes is present witha magenta coupler in the emulsion is important.

Sensitizing dyes are further required to leave no color stain in thephotographic light-sensitive materials after development. In general, asensitizing dye leaves color stains in the image-bearing emulsion layersand/or subsidiary layers (intermediate layers, etc.,) or on thedeveloped and fixed support. Such a harmful influence due to remainingdyes must be corrected by photographic means used in the photo-engravingprocess, such as a color masking method, and such a color correction isparticularly troublesome in the case of a lithographic photographicnegative which must have a light grey color. This effect of theremaining dyes is also undersirable in photographic papers since in thecase of black and white photographic papers a bright white color is notobtained, and in the case of color photographic papers true colorreproduction becomes impossible.

Further, if a yellow or magenta color (or a yellow or magenta dye) dyeremains other difliculties occur, e.g., when a part of a finishedphotograph is exposed to sun light the dyes at that portion are bleachedby the sun light, which results in a partially bleached and partiallycolored image. Consequently, in the case of sensitizing photographicemulsions using sensitizing dyes, it is important to prevent thesensitizing dyes from remaining in the finished photographic paper,lithographic film, or other photographic film or plate.

Moreover, the sensitizing dyes used are also required to give aspectrally sensitive region sufiiciently stable to a safe light which isis used in processing light-sensitive materials. For color photographiclight-sensitive materials, in particular color positive films or colorpapers, a safe light having a maximum percent transmission at about570-620 m is generally used. Therefore, the long wave length side of thespectrally sensitive region of a greensensitive emulsion layer thussensitized has usually been sharply cut so that the emulsion layer isstable under the safe light. If this is not done, fog is formed by theaction of the safe light to cause stains on the finished photography.

SUMMARY OF THE INVENTION One object of the present invention is toprovide a silver halide photographic emulsion supersensitized by acombination of sensitizing dyes which leave less residual dyes or colorsin the finished photographic product.

Another object of this invention is to provide a silver halidephotographic emulsion supersensitized by a combination of sensitizingdyes, the special sensitivity of which is not reduced during the storageof the silver halide emulsion thus sensitized, as well as during storageof photographic light-sensitive materials having layers of the silverhalide emulsions thus sensitized, even when the silver halide emulsionor emulsion layer further contains compounds with one or more anionicgroup(s), such as a gelatin precipitant (as set forth in US. Pats.3,138,461, 3,241,-

3 969, 3,366,482, 3,455,694, 3,522,053, British Pat. 1,103,- 420, GermanPat. 1,238,370 etc.), an anionic activating agent (as set forth in US.Pats. 3,003,877, 3,026,202, 3,201,252, 3,415,649, etc.) or a colorcoupler such as a magenta coupler (refer, for example, to P. GlafkidisPhotographic Chemistry, vol. II pp. 596-615).

BRIEF DESCRIPTIONOF THE DRAWING The drawing is a graph showing thespectral percent transmission curve of a safe light filter.

DETAILED EXPLANATION OF THE INVENTION The above and other objects ofthis invention are attained by using the combination of selectedbenzimidazolo.oxacarbocyanine dyes and selected oxacarbocyanine dyes.The combination of such dyes provides a valuable technical advance inthe production of photographic emulsions.

Further objects of this invention will become apparent from thefollowing descriptions of the specification.

The benzimidazolo.oxacarbocyanine dyes used in this invention arerepresented by the following general formula wherein A and A eachrepresents a hydrogen atom, a halogen atom (e.g., a chlorine atom, abromine atom, a fluorine atom, an iodine atom), a hydroxyl group, analkoxyl group (e.g., a methoxy group, an ethoxy group), an amino group(e.g., an amino group, a methylamino group, a dimethylamino group), anacylamido group (e.g., an acetamido group), an acyloxyl group (e.g., anacetoxyl group), a carboalkoxyl group (e.g., a carboethoxy group), analkoxycarbonylarnino group (e.g., an ethoxycarbonylamino group), a cyanogroup, a trifiuoromethyl group, an alkoxycarbonyl group (e.g., amethoxycarbonyl group, an ethoxycarbonyl group), an alkyl sulfonyl group(e.g., a methylsulfonyl group), a sulfamyl group, an alkylaminosulfonylgroup (e.g., an ethylarninosulfonyl group, a diethylaminosulfonylgroup), a morpholinosulfonyl group, a piperidinosulfonyl group, amorpholinocarbonyl group, a carbomoyl group or an alkylcarbonyl group.

A and A each represents a hydrogen atom, a lower alkyl group preferablyhaving up to 4 carbon atoms (e.g., a methyl group, an ethyl group, ann-propyl group), a halogen atom (e.g., a chlorine atom, a bromine atom,a fluorine atom, an iodine atom), an alkoxyl group (e.g., a methoxygroup, an ethoxy group), a hydroxyl group, a phenyl group (e.g., aphenyl group, a p-sulfophenyl group), a carboxyl group, analkoxycarbonyl group (a methoxycarbonyl group, an ethoxycarbonyl group),a cyano group, a trifuoromethyl group, an amino group (e.g., an aminogroup, a methylamino group, a dimethylamino group), an acyl group (e.g.,an acetyl group), an acyloxyl group (e.g., an acetoxyl group), analkoxycarbonylamino group (e.g., an ethoxycarbonylamino group) or acarboalkoxyl group (e.g., a carboethoxy group).

R, R and R each represents an alkyl group which implies an unsubstitutedalkyl group preferably having up to 6 carbon atoms or a substitutedalkyl group as is conventionally used as an N-substituent of asensitizing cyanine dye (e.g., a methyl group, an ethyl group, annpropyl group, a vinyl methyl group), a hydroxyalkyl group (eg, aZ-hydroxyethyl group, 4-hydroxybutyl group), an acetoxyalkyl group(e.g., a 2-acetoxyethyl group, a 3- acetoxypropyl group), an alkoxyalkylgroup (e.g., a 2- methoxyetheyl group, a 4-butoxybutyl group), acarboxyalkyl group (e.g., a 2-carboxyethyl group, a 3-carboxypropylgroup, a 2-(2-carboxyethoxy) ethyl group), a piii carboxy aralkyl group(e.g., carboxybenzyl group), a sulfoalkyl group (e.g., a Z-sulfoethylgroup, a 3-sulfopropyl group, a 3-sulfobutyl group, a 4-sulfobutylgroup, a 2- hydroxy-3-sulfopropyl group, a 2-(3-sulfopropoxy)ethylgroup, a 2-acetoxy-3-sulfopropyl group, a3-methoxy-2-(3-sulfopropoxy)propyl group, a 2-(3-sulfopropoxy)ethoxyethyl group, a 2-hydroXy-3-(3'-sulfopropoxy)propyl group, ap-sulfophenethyl group and a p-sulfobenzyl group) or an aralkyl group(e.g., a benzyl group, a phenylethyl group).

In the above definitions, however, at least one of R and R must be alkylgroup having a sulfo group or an alkyl group having a carboxyl group.

X represents an anion such as a chloride ion, a bromide ion, an iodideion, a thiocyanate ion, a sulfate ion, a perchloride ion, ap-toluenesulfonate ion, a methylsulfate ion or an ethylsulfate ion.Finally, n represents 1 or 2, n being 1 when the dye forms anintramolecular salt (betaine-like structure).

The oxacarbocyanine dyes used in this invention are represented by thefollowing general formula (II) II wherein B B B and B each has the samemeaning as A or A in general formula (I) R represents a hydrogen atom, alower alkyl group preferably having up to 4 carbon atoms (e.g., a methylgroup, an ethyl group), or an aryl group (e.g., a phenyl group).

R and R each has the same meaning as R and R in general formula (1), Xhas the same meaning as X and m has the same meaning as n.

Typical examples of benzimidazolo-oxacarbocyanine dyes as are used inthe present invention are shown below for purposes of illustration, butsuch examples should not be taken to limit the sensitizing dyes used inthis invention.

Typical examples of the oxacarbocyanine dye used in this invention areshown below for purposes of illustration. However, the sensitizing dyesused in this invention v are not limited thereto.

II-S

II-ll.

HaCOOC (nnhsor (CHI) as 0 a 0 115 -CH=&CH= COO-CH; N N

l 2) a 0 a (CH2) 3S 0 11 QCCI-Is N t 0 O CH:

CH=J3CH= 113 N C1 2) asQs bnznsoanuj H 0 CH; N N

((EHz) aSOr ((EHz) 350311 The first feature of this invention is that abetter supersensitization eifect is obtained using a combination of thebenzimidazolo.oxacarbocyanine dye represented by general formula (I) andthe oxacarbocyanine dye represented by general formula (II). A markedlyhigh spectral sensitivity is obtained in particular when at least one ofthe 5-position or the 6-position of the benzimidazolo nucleus in generalformula (I) is substituted with a halogen atom and the 5-position of thebenzoxazole nucleus in general formula (II) is substituted with ahalogen atom or an alkoxyl group.

The second feature of this invention is that when a combination of thesensitizing dyes of this invention is used, the residual color or dyesbased on the sensitizing dyes in the processed photographic elements arelessened. Among conventional sensitizing dyes, sensitizing dyes whereall of the nitrogen atoms of the heterocyclic ring have been substitutedby lower alkyl groups, such as the comparison dyes A and B shown below,tend to leave a large amount of color stain or residual dyes in theprocessed photosensitive elements. In particular, when the processingtime is short, the extent of color stain or residual dyes is large. Onthe other hand, because in the sensitizing dye represented by generalformula (I) used in this invention at least one of R and R which are thesubstituent groups of the nitrogen atoms of the heterocyclic ring, is analkyl group having a sulfo group or an alkyl group having a carboxygroup. the amount of color stain or residual dye is extremely low.Further, the sensitizing dye of general formula (II) also gives very lowcolor stain. Accordingly, a combination of both types of sensitizingdyes gives a silver halide photographic emulsion having a very lowdegree of color stain.

The third feature of this invention is that when the combination of thesensitizing dyes of this invention is used together with anioniccompounds which usually degrade the spectral sensitizing action, such asa light-absorbing dye having a sulfo group in the chemical structure, agelatin precipitant having a sulfo group, or a coupler for colorphotographic elements, the combination of dyes of this inventionnonetheless imparts a high sensitivity to the silver halide emulsion.

It is generally believed that a sensitizing dye having a nitrogen atomin a heterocyclic ring which is substituted by an alkyl group having asulfo group or an alkyl group having a carboxy group gives, when presenttogether with a color coupler, a high sensitivity. However, it has beenobserved that the sensitizing dyes represented by general formula (I) orthe sensitizing dyes represented by general formula (II) have almost nospectral sensitizing effect when these sensitizing dyes are usedindividually with a color coupler. Therefore, it is quite astonishingthat when a combinaton of sensitizing dyes represented by the generalformula (I) and general formula (II) is used with a color coupler, ahigh spectral sensitivity is obtained.

The fourth feature of this invention is that when a combination of theaforesaid senstizing dyes of this invention is used together with acoupler for color photographic elements in a silver halide emulsion thespectral sensitivity of the silver halide emulsion thus sensitized isnot substantially reduced during storage of the silver halide emulsionor during storage of photosensitive elements containing such a silverhalide emulsion.

The fifth feature of this invention is that by using sensitizing dyesselected from dyes represented by general formulae (I) and (H) aspectral sensitivity stable to a safe light as is usually employed forprocessing" color positive films and color photographic papers isobtained. supersensitizing combinations of certain kinds of oxacar- Ibocyanine dyes and certain kinds of benzimidazolocarbocyanine dyes areknown, as disclosed in Japanese Patent Publication No. 2,288/ 1968. Thebenzimidazolocarboxyanine dye showing the most remarkablesupersensitizing effect among the dyes described in the above JapanesePatent has a benzimidazole nucleus substituted at the 5- and 6-positionsthereof by a chlorine atom, and the sensitization maximum of the dye isat about 5 80 mg, although this maximum varies somewhat according to thenature of the silver halide emulsion to be employed. Also, abenzimidazolocarbocyanine dye having a benzimidazole nucleus substitutedby a chlorine atom at the 5-position has a sensitization maximum at alonger wave length than 570 mu.

Accordingly, in the case of using the aforesaidbenzimidazolocarbocyanine dye in which the 5- and 6-position of thebenzimidazole nucleus have been substituted by a chlorine atom or inwhich the 5-position of the benzimidiazole nucleus has been substitutedby a chlorine atom in a combination with the oxacarbocyanine dyesdescribed in the above Japanese Patent, such a combination gives severefog under a safe light as is used for color positive films or colorphotographic papers, thereby making the use of such a sensitizingcombination impractical even when a small amount of thebenzimidazolocarbocyanine dye is used, for instance, even when thebenzimidazolocarbocyanine dye is used in an amount of A by weight of theamount of the oxacarbocyanine dye.

On the other hand, the benzimidazolo, oxacarbocyanine dye of thisinvention represented by. the general formula (I) in which the 5- and6-positions have been substituted by a chlorine atom has itssensitization maximum at about 565 m at the longest, and thus aphotographic emulsion containing the dyes of this invention can besafely used under a safe light, i.e., it is stable.

The dyes of general formula (I) are described in, e.g., Japanese PatentPublication No. 14,030/1969 (filed on Jan. 18, 1966), etc., and may bereadily synthesized by referring to the descriptions of the above patentor may be synthesized by methods similar to the methods described inthat specification.

The dyes of general formula (II) aredescribed in, e.g., iFrench Pat.1,108,788; U.S. Pat. 2,503,776; and British Pats. 840,223 and 841,119.These sensitizing dyes may be readily synthesized by referring to thedescriptions of these patents or may be synthesized by methods similarto those described in the recited patents.

The silver halide used in the photographic emulsion in this inventioncan be selected from among those commonly used in the photographic arts,for instance, silver chloride, silver bromide, silver iodide, silverchlorobromide, silver iodobromide, or silver chloroiodobromide.

However, the invention is quite advantageously used with a silver halidephotographic emulsion containing silver chlorobromide or silverchloroiodobromide. In a silver chlorobromide emulsion, it isparticularly advantageous to further add thereto a water-soluble iodidein an amount of, e.g., 0.0050.10 mole per mole of AgCl of the silverhalide, or a water-soluble bromide in an amount of, e.g. 0.01-0.20 moleper mole of AgCl of the silver halide in the silver halide emulsionafter forming the silver halide. Of course, a mixture of a water-solublebromide and a water-soluble iodide may be added to the emulsion. It iseffective to add the water-soluble halide(s) to the emulsion aftersubstantial completion of chemical ripening and especially preferred toadd the halide(s) after completion of chemical ripening, followed by theaddition of the sensitizing dyes.

In the present invention a gelatino silver halide emulsion is ordinarilyused, but other materials known to be equivalents in the art which haveno harmful influence on the photosensitive silver halides, for instance,gelatin derivatives such as phthalated gelatin or malonated gelatin,albumin, agar agar, gum arabic, alginic acid, a watersoluble starch suchas dextrin, a hydrophilic resin such as polyvinyl alcohol, polyvinylpyrrolidone, polyacrylamide, or polystyrene sulphonic acid, or cellulosederivatives such as hydroxyethyl cellulose or carboxymethyl cellulosemay be used instead of gelatin, or as mxitures thereof.

A supersensitizing amount of the sensitizing dyes of general formula (I)and general formula (11) may be used in various concentrations thereof,according to the nature of the silver halide emulsion, the concentrationof silver halide in the emulsion and the desired effect.

The optimum concentartions of the sensitizing dyes may be determinedaccording to known methods, e.g., by dividing a silver halide emulsioninto several portions, incorporating in each portion the sensitizingdyes in different concentrations, and measuring the sensitivity ofemulsion. The optimum concentrations of the supersensitizing combinationof the dyes in this invention can also be easily determined according tothe above method.

The sensitizing dyes may be incorporated in a silver halide emulsion byany manner well known in this art in the present invention. For example,the sensitizing dyes may be directly dispersed in a silver halideemulsion or may be incorporated therein as a solution in pyridine,methanol, ethanol, methyl Cellosolve, acetone or a mixture of suchmaterials, or in water. The organic solvent solution of the sensitizingdyes may, if necessary, be diluted with water. The dissolution of thesensitizing dyes may be conducted using ultrasonic vibrations. Moreover,the methods described in the specifications of Japanese Pats. 8,231/1970, 2,389/1969, 27,555/1969, and 22,948/ 1969; German Pat. 1,947,935;and U.S. Pats. 3,485,634, 3,342,605, and 2,912,343, can also be usedwith success.

The sensitizing dyes may be dissolved separately in suitable solventsand the solutions may be separately added to a silver halide emulsion.Alternatively, the sensitizing dyes may be dissolved separately in thesame or different solvents and the solutions may be mixed before theincorporation thereof in the silver halide emulsion. It is necessary touniformly disperse the dyes throughout the silver halide emulsion priorto coating the emulsion containing the sensitizing dyes on a supportsuch as a glass sheet, a cellulose derivative film, a polyvinyl resinfilm (such as a polystyrene film or a polyvinyl chloride film), apolyester fihn, a synthetic paper, a baryta coated paper, or apolyolefin-coated paper. The sensitizing dyes may be added to the silverhalide emulsion at any time during the preparation of the emulsion, butare preferably added after the completion of the second ripening.

The supersensitizing ratio of the sensitizing dye of general formula (I)to the sensitizing dye of general formula (II) is not limited in thisinvention, but the preferred ratio of dye (I) to dye (II) is in therange of from about 9/1 to about 1/9 by weight, and is varied accordingto the desired end use. The amounts of the sensitizing dyes used may bechanged according to the nature of each silver halide emulsion and thedesired effect. In general, optimum sensitivity is obtained byincorporating each sensitizing dye in an amount of from about 1 10- toabout 5 10- moles per gram mole of silver halide. In general, too smallor too great an amount of the dye added decreases or does not increasethe sensitivity of the emulsion.

The silver halide photographic emulsion of this invention may also besensitized by any other well known procedure, i.e., by a noble metalsensitizer (see U.S. Pats. 2, 540,085, 2,597,856, 2,597,915, 2,399,083,etc) a sulfur sensitizer (see U.S. Pats. 1,574,944, 2,278,947,2,440,206, 2,410,689, 3,189,458, 3,415,649, etc.), a reductionsensitizer (see U.S. Pats. 2,518,698, 2,419,974, etc.), or analkyleneoxide sensitizer, or by combinations thereof. The silver halideemulson may contain, if desired, an antifoggant such asnitrobenzimidazole, or ammonium chloroplatinitc a subilizer such as4-hydroxo-6-methyl-1,3,3a,7- tetrazaindene, a hardening agent such asformaldehyde, chromalum, 1-hydroxo-3,S-dichlorotriazine soda, glyoxal ordichloroacrolein, a Wetting agent such as saponin, or sodium alkylbenzenesulfonate, a plasticizer, a development accelerator and an airfogging preventor.

Examples of the sulfur sensitizers are allylthiocarbamide, thiourea,sodium thiosulfate and cystin.

Examples of the noble metal sensitizers are potassium chloroaurate,aurousthiosulfate and potassium chloropalladate.

Examples of the reduction sensitizers are tin chloride, phenylhydrazineand reductone.

The color couplers preferably used in this invention are described inthe specifications of, e.g., U.S. Pats. 2,600,788 and 2,801,171; BritishPat. 904,852; Japanese Pat. 6,031/ 1965; etc.

The following 'known couplers are exemplary of those used in thisinvention in combination with the sensitizing. dyes of general formulae(I) and (II):

(5) /N=G-NHC OCHzCH C15H37 Q, CCH3 N= CNH C O NHCOGH CmHaa C-CH: H S 03H0 N: C-NH C O- Q cmooon NHCOH-CH=CHC H 3 fill-CH3 0 0 ONE cmcmcmomoGeunm) (9) sHirG) c1 m o (0 n) on 01 NHCOCHz-O- sHM NH O 0 CHICHQCHj-Os nm 12 on I NHC O-Q a nG) mo nncoon=-o-mm n 01 NHCOCH-CH=CH-Cmfiu H3Omooon @jc ONHCnHn (15) on p c omrcmcrn-Q-rmc 0111135 0 onncmcm-Q-mr cOCHa-CH-CraHss to 0H crno 0 on H33CuCH-HC ONE OCH:

ocmoonrr Halon-C ONH C O OH c ocmc ONE c 0 one ONHQ- NHCO CH-CsH1 (L-QO51111 -cocmoonn -s 0.N

- CH2CH2CHF Q-cocmoomrO-oom nncocrwo-Q-cmm s nU ( 5O Q-cocmcomr-NHCOCHz-O C5 u( OCH; 5 11) The symbol (t) in the above formulae, whereused, in-

Example 1 A series of multi-layer color photographic films were preparedas follows employing the sensitizing dyes shown in Table 1 in thegreen-sensitive emulsion layer: a blue sensitive gelatino silveriodobromide emulsion (I:Br ratio 1 mol percent: 99 mole percent) layer(100 g. of gelatin and 0.57 mol of Ag per kg. of emulsion) was subjectedto sulfur sensitization and gold sensitization by the addition theretoof 2.0 mg of Hypo and 2.0 mg. of potassium tetrachloroaurate (III) permole of silver halide, and then directly applied to a film support; asilver chlorobromide (Cl:Br ratio 55 mole percent: 45 mole percent)gelatin emulsion g. of gelatin and 0.57 mol of Ag per kg. of emulsion)spectrally sensitized by the following dye in the red region and furthersubjected to sulfur sensitization and gold sensitization in the samemanner as described above was applied to the blue-sensitiveemulsionlayer; Red sensitizing dye:

a silver chlorobromide emulsion as described above which was greensensitized was spcctrally sensitized by a combination of dye I-lOheretofore described in an amount of 200 mg. per mole of silver and adye A or 9-ethyl-3,3- diethyl-S,5'-diphenyloxacarbocyanine bromide, acomparison dye outside the scope of this invention, in an amount of 100mg. per mole of silver and sensitized by sulfur and gold in the samemanner as described above in Example 1 was further applied to the silverhalide emulsion layer. The green-sensitive emulsion layer furthercontained about 5 g./1 kg. of emulsion of the anthraquinone dye havingthe structure (see the specification of U.S. Pat. No. 2,865,- 752) shownbelow as a light absorbing dye. Two other multi-layer color photographicfilms were also prepared in the same manner except employing the supersensitizing combinations of this invention shown in Table 1 instead ofthe combination described above.

A sample of each color photographic film prepared as above was exposedthrough an optical wedge to green light from a tungsten source of 2854K. through a SP-2 filter (trade name, made by Fuji Photo Film Co.) for$4 of a second by means of a sensitometer made by Fuji Photo Film Co.and then subjected to the following processings. The density of the filmsample thus processed was measured to determine the green relativesensitivity and the density of contamination.

Irradiation preventing dye:

NBC SH; ONE 0 NHCHZS C Na NtiC SHqCHlk NHCHQSOaNB 1 The composition ofthe color developer was as follows:

G. Sodium hexametaphosphate 2.0 Sodium sulfite (anhydrous) 4.02-amino-5-dlethylnmine toluene monohydrochloride 3.0 Sodium carbonatemonohydrate 20.0 Potassium bromide 2.0

Water to make 1 liter.

2 The compositions of the fixing solution and the bleaching solution arealso conventional.

The green sensitivity was determined based on the value of log E plottedagainst 1.0 above fog-density of the Control.

It is seen from Table 1 that the photographic elements containing thecombination of sensitizing dye I- and sensitizing dye 11-4 orsensitizing dye II-2 were superior with respect to green relativesensitivity and density of contamination as compared to the photographicelement containing the control combination of sensitizing dye I- 10 andsensitizing dye A. The 9-ethyl-3,3'-diethyl-5,5'-diphenyloxacarbocyanine bromide, as compared with the dye of the presentinvention, is of low sensitivity and produces a high contaminationdensity when the compound is photographically treated.

The density of contamination is the value obtained by measuring thedensity of the processed sample through a green filter by means of aself-recording densitometer made by Fuji Photo Film Co., Ltd..

Example 2 Samples of single layer color photographic films were preparedusing the basic procedure described in Example 1 employing, however,different supersensitizing combinations as shown in Table 2. Each samplewas prepared by applying to a film support a silver iodochlorobromideemulsion (100 g. of gelatin and 0.57 mol Ag/kg. of emulsion; I:Br:C1ratio 1 mole percent:39 mole percentz60 mole percent) containing adispersion of the pyrazolone magenta coupler (1) hereinbefore set forthin an amount of 800 g. per 1 kg. of emulsion and was subjected to asulfur sensitization and gold sensitization as described in Example 1.The samples were compared as to extent of contamination and change insensitivity by allowing them to stand.

In this case, one sample of each series was prepared by immediatelyapplying the silver halide emulsion to the support, while another samplein the series was prepared by applying the silver halide emulsion to thesupport after allowing the emulsion to stand for 3 hours at 40 C. Eachof the samples was exposed and processed as in Example 1. The results ofsensitometric and stain or contamination measurements are shown in Table2. In Table 2 the density of contamination is shown by the valueobtained by measuring the density of the processed sample through agreen filter by means of a self-recording densitometer made by FujiPhoto Film Co., Ltd. A and B in Table 2 are dyes outside the scope ofthis invention.

The results shown in Table 2 establish that the silver halide emulsionof this invention has excellent sensitivity as compared to thecomparison samples, and that the silver halide emulsion showed lessreducton in sensitivity 7 1 6 Example 3 Samples of single layer colorphotographic elements containing a coupler were prepared in the samebasic manner as in Example 2 while employing different supersensitizingcombinations as shown in Table 3. The samples were compared with respectto stability to a safe light.

The samples used in this example were prepared by applying a silverchlorobromide emulsion containing a dispersion of the same pyrazolonemagenta coupler as was used in Example 2 in the amount which was used inExample 2, which had been subjected to sulfur sensitization and goldsensitization as described. Of each sample, one was exposed for 30seconds to light passed through a safe light filter and then processedas in Example 1.

On the other hand, another sample was processed as in Example 1 withoutexposure to the safe light. The density of the sample films thusprocessed was then measured using a green filter by means of aself-recording densitometer made by Fuji Photo Film Co., Ltd. Bycomparing these exposed samples to the sample not exposed to the safelight it was found that the samples used in the tests had almost nostains or contamination.

Comparison dye C used in this example was anhydrol,1'diethyl-3,3-disulfobutyl-5 ,5 ',6,6-tetrachlorobenzimidazolo-carbocyaninehydroxide.

The results are shown in Table 3.

TABLE 3 Green Fog density relative under sate sensitizing dye (mg. permole of Ag) sensitivity light 0 (20) +II2(300) 89 0. 22 C (30)+II2(300)0. 42 0. 06 132 0. 06

From the results shown in Table 3, it is clear that when comparison dyeC was used in place of sensitizing dye I-l0 or I-17 in thesupersensitizing combination, the silver halide emulsion was sensitizedspectrally to the longer wave length side, and thus the sample filmprepared using such a silver halide emulsion had an extremely low(safety) stability to a safe light.

The supersensitizing etfect obtained from the combination of thesupersensitizing dyes according to the present invention will be furtherexplained by the following examples of this invention.

Example 4 A silver chlorobromide emulsion containing 0.57 mol of Ag perkg. of the emulsion (Cl: 55 mol percent, Br: 45 mol percent) prepared inan ordinary manner was divided into several parts and each part ofsilver halide emulsion was sensitized by the combination of sensitizingdyes shown in Table 4.

The dyes were dissolved in a solvent therefore, such as methanol andwater, and the solution added to the silver halide emulsion. Theemulsion Was maintained at 40 C. for 10 minutes and then applied to afilm support.

The film sample was then dried, exposed through an optical wedge and aFuji Filter SC-52 (trade name, made by Fuji Photo Film Co., Ltd.) bymeans of a sensitometer made by .Fuji Photo Film Co., Ltd. and developedin a developing solution having the following composition:

G. Metol 0.31 Anhydrous sodium sulfite 39.6 Hydroquinone a 60Anhydroussodium carbonate 18.7 Potassium bromide 0.86

Citric acid 0.68 Potassium metabisulfite 1.5

Water added to make 1 liter.

17 A sample film thus developed was fixed in an acid hardening fixingbath having the following formula, rinsed, and dried.

B solution is slowly added to the A solution with stirring. Then, wateris poured into the resulting mixture to make the volume 1 liter.

The relative sensitivity and fog of each of the samples thus processedwere measured and the results are shown in Table 4 together with thesensitization maximum.

The results of control samples prepared by using the same silver halideemulsion as above but containing only one of the sensitizing dyes andprocessed in the same Way as above are also shown in Table 4 for thesake of comparison.

As is clear from the results shown in Table 4, by using thesupersensitizing combinations of this invention, remarkably highersensitivities were obtained than in case of using the corresponding dyesindividually.

Example 5 After adding the sensitizing dye or dyes shown in Tabl 5 to asilver halide emulsion as in Example 4, an aqueous solution of potassiumiodide (6X 10- moles per mol of silver) was added to the emulsion. Theresultant silver halide emulsion was maintained at 40 C. for 10 minutesand then applied to a film support. The sample films thus prepared wereexposed and processed as in Example 4.

The relative sensitivity and fog of the samples thus processed weremeasured and the results are shown in Table 5 together with thesensitization maximum.

TABLE 5 Relative Sensitiza- Sample sensitizing dye (mg. sensitionmaxinumber permole of Ag) tivity Fog mum (m 100 0.05 About 552. 105 0.05About 556. 135 0.05 Apout 555. 102 0.07 About 561. 100 0.05 About 552.148 0.05 About 560. 141 0.05 Do. 129 0.08 Do. 100 0.06 About 550. 1660.05 About 560.

From the above table, it is clear that the sensitivities obtained usingthe supersensitizing combinations of this inventon were remarkablyhigher than the cases of using the corresponding sensitizing dyesindividually.

While the invention has been described in detail and with reference tospecific embodiments thereof, it will be apparent to one skilled in theart that various changes and modifications can be made therein withoutdeparting from the spirit and scope thereof.

18 What is claimed is: 1. A silver halide photographic emulsioncomprising a supersensitizing amount of at least one benzimidazolo.oxacarbocyanine dye represented by general formula (I') and at least oneoxacarbocyanine dye represented by general formula (II) (II) B1 0 R 0 Umat=w 1 v B1 N Iii B i l 2')m-1 wherein A and A each represents ahydrogen atom, a halogen atom, a hydroxyl group, an alkoxyl group, anamino group, an acylamido group, an acyloxyl group, analkoxycarbonylamino group, a cyano group, a trifluoromethyl group, analkoxycarbonyl group, an alkylsulfonyl group, a sulfamyl group, analkylaminosulfonyl group, a morpholinosulfonyl group, amorpholinocarbonyl group, a piperidinosulfonyl group, a carbamoyl group,or an alkylcarbamoyl group; A and A each represents a hydrogen atom, alower alkyl group, a halogen atom, an alkoxy] group, a hydroxyl group, aphenyl group, a carboxyl group, an alkoxycarbonyl group, a cyano group,a trifiuoromethyl group, an amino group, an acylamido group, an acylgroup, an acyloxyl group, an al'koxycarbonyl group, or a carboalkoxylgroup; B B B and B, have the same meaning as A and A R, R and R eachrepresents an alkyl group; at least one of R and R being a sulfoalkylgroup or a carboxyalkyl group; R represents a hydrogen atom, a loweralkyl group or an aryl group; R and R have the same meaning as R and R Xrepresents an anion; m and n each represents 1 or 2; said dyes formingan intramolecular salt when m and n are 1; and X represents an anion.

Y 2. The silver halide photographic emulsion as set forth in Claim 1wherein the halogen atom is chlorine, bromine, fluorine or iodine; thealkoxy group is methoxy or ethoxy; the amino group is an amino group,methylamino or dimethylamino; the acylamido group is an acetoamidegroup; the acyloxyl group isan acetoxy group; the carboalkoxy group is acarboethoxy group; the alkoxycarbonyl amino group is an ethoxycarbonylamino group; the alkoxycarbonyl group is a methoxycarbonyl orethoxycarbonyl group; the alkylsulfonyl group is a methylsulfonyl group;the alkylaminosulfonyl group is ethylaminosulfonyl ordiethylaminosulfonyl; the lower alkyl group is methyl, ethyl orn-propyl; the phenyl group is phenyl group'or p-sulfophenyl, in each Aor A or A and A and wherein the alkyl group is methyl, ethyl group,npropyl, vinylmethyl, hydroxyalkyl, acetoxyalkyl, alkoxyalkyl, alkylhaving a carboxy group, alkyl having a sulfo group or aralkyl in each R,R and R or R and R 3. The silver halide photographic emulsion as setforth in Claim 2 wherein the hydroxy alkyl group is Z-hydroxyethyl or4-hydroxbutyl; the acetoxy alkyl group is 2-acetoxyethyl or3-acetoxypropyl; the alkoxyalkyl group is 2-methoxyethyl or4-butoxybutyl; the alkyl group having a carboxy group is 2-carboxyethyl,3-car-boxypropyl, 2- (2-carboxyethoxy)ethyl or p-carboxybenzyl; thealkyl group having a sulfo group is 2-sulfoethyl, 3-sulfopropyl,3-sulfobutyl, 4sulfobutyl, 2-hydroxy-3-sulfopropyl, 2-(3-sulfopropoxy)ethyl, 2-acetoxy-3-sulfopropyl, 3-methoxy-2-(3-sulfopropoxy)pr0pyl, 2-[2-(3-sulfopropoxy)ethoxy] ethyl, 2-hydroxy3-(3-sulfopropoxy)propyl, sulfophen- 1 9 ethyl or p-sulfobenzyl; and thearalkyl group is benzyl or phenethyl.

4. The silver halide photographic emulsions as set forth in Claim 1wherein there is present a binder of the emulsion comprising gelatin.

5. The silver halide photographic emulsion as set forth in Claim 1wherein the ratio by weight of dye (I) to dye (II) is in the range offrom about 9/1 to about 1/9.

6. The silver halide photographic emulsion as set forth in Claim 1wherein the amount of the sensitizing dye added to the emulsion is inthe range of from about 1 10 to about 5 X 10' moles per gram-mole halidein the emulsion.

7. The silver halide photographic emulsion as set forth in Claim 1wherein the silver halide is silver chlorobromide or silverchloromoiodide.

8. The silver halide photographic emulsion as set forth in Claim 7wherein the silver halide is silver chlorobromide.

9. The silver halide photographic emulsion as set forth in Claim 8wherein said silver halide emulsion further contains an iodide in anamount of 0.005-0.l mole and/or a bromide in an amount of 0.01-0.20 molrespectively, per mole of silver chloride constituting the silverhalide.

10. The silver halide photographic emulsion as set forth in Claim 1wherein said silver halide photographic emulsion contains a colorcoupler.

11. The silver halide photographic emulsion as set forth in Claim 10wherein the color coupler is a magenta coupler.

12. The silver halide photographic emulsion as set forth in Claim 1wherein said silver halide photographic emulsion contains a lightabsorbing dye.

13. The silver halide photographic emulsion as set forth in Claim 1wherein said benzimidazolo.oxacarbocyanine dye represented in generalformula (I) is substituted by a halogen atom in at least one of the or6-positions of the benzimidazole nucleus thereof.

14. The silver halide photographic emulsion as set forth in Claim 1wherein said oxacarbocyanine dye represented by general formula (II) issubstituted by a halogen atom at the 5-position of the benzoxazolenucleus thereof.

A color photographic light-sensitive element comprising a support havingthereon a layer of the silver halide photographic emulsion as set forthin Claim 10.

16. The silver halide photographic emulsion containing asupersensitizing amount of the combination selected from the group ofand HgCHzSOaH zCHaSOa' (2) I v N O =CH-CH=CH 5 III N (CH :SOSNaCHZGIII-"(FHCH3 S 03" and 2 5 CH-J]: C H- 15 C1 Cl N N JHflgSOzH as 03-I C H CH: CH- (11 -o1 N N lgHs JH S 0 3- and O O CzHs C H 4}: CH

Cl Cl N N (I-I?) is 0 3H (Hz) 3S 0 3' C H=C H-C H:

03 03" 93 03 and O O (llzHs =CH-C=CH Cl Cl N N dmsoH dinso- 9 a a a a-CH=C H-CH= 1 I N 0 on:

( 2) as 03' JzH and O O C2H5 =CH(E=CH N 1 1 5 AHICHQSOQH HzCHzSOa'(R2115 N 0 G1 =C H-QE-CIH- o1 l I) B CtNa JH CH fiZHCH 21 22 andReferences Cited UNITED STATES PATENTS 0 0,11, 0 3,397,060 8/1968 Schwanet a1. 96-124 l 5 3,580,724 5/1971 Sato et a1. 96-124 H300 3,663,2105/1972 Sato et a1. 96-124 3 3,713,835 1/1973 Sato et a1. 96137 I(CHQMSOJH (AHMSOS' J. TRAVIS BROWN, Primary Examiner 17. Thephotographic emulsion of Claim 9 wherein the 10 iodide and/ or bromideare water-soluble. 9684, 100, 137

